Foamable particulate styrene polymers for the production of moldings exhibiting good dimensional stability and good fusion

ABSTRACT

The invention relates to foamable particulate self-extinguishing styrene polymers which, on account of their low content of oxyalkylation product of ammonia or amine, are suitable for making foam articles exhibiting good fusion and good dimensional stability, and to a process for their production.

United States Patent Nintz et 'al.

all of Germany Assignee: Badische Auilin & Soda-Fabrik Aktiengesellschaft, Ludwigshafen/Rhine, Germany Filed: Jan. 31, 1972 Appl. No.: 222,327

Foreign Application Priority Data Feb. 3, 197i Germany P 21 04 867.9

US. Cl 260/2.5 B, 260/2.5 FP, 260/459 R, 260/DIG. 24

[451 Aug. 28, 1973 [51] Int. Cl. C08j 1/18 [58] Field of Search 260/2.5 FP, DlG. 24, 260/459 R, 2.5 EP

References Cited UNITED STATES PATENTS 9/1966 Ingram 260/25 FP 4/1972 Cyba 260/25 EP Primary Examiner-Murray Tillman Assistant Examiner-Morton Foelak Attorney-Johnston, Root, OKeeffe, Keil, Thompson & Shurtleff [57] ABSTRACT The invention relates to foamable particulate selfextinguishing styrene polymers which, on account of their low content of oxyalkylation product of ammonia or amine, are suitable for making foam articles exhibiting good fusion and good dimensional stability, and to aprocess for their production.

2 Claims, No Drawings "ticulate styrene polymers are first heated with steam or hot' gases to temperatures above their softening point to form a loose material. This step is referred to as pre-expansion. The pre-expanded styrene polymers are then stored for a'time, after which they are further expanded in a pressure-resistant mold which is not gastight when closed by -reheating with steam such that the particles fuse together to form a molding whose dimensions correspond to the cavity of the mold. This second step is known as molding. After molding, the resulting article is cooled in the'mold. Cooling must be continued until the interior of the molding has reached a temperature below the softening point. If the molded' article is removed from the mold too soon, it may be deformed. As foamed plastics materials are good insulators, relatively long cooling periods are required to cool the moldings. The periodwhich elapses before a molding canbe removed from the mold without there being any subsequent deformation is usually referred to as the minimum residence time in the mold.

After removal from the mold, the molding is usually stored for a time until it has completely cooled, after which it may, if it is a block for example, be cut up into foam boards for insulating purposes.

' During this final cooling period, the sides of the block become concave to acertain extent. This is particularly noticeable'in the case of the surfaces which have been directly exposed tothe steam and thedegree of shrink age'may be several percent. I

In particular, shrinkage at the sides is relatively pronounced and the foamed styrene polymer particles exhibit relatively poorfusion when the styrene polymer used is one which has been prepared in the presence of "oxide,propylene oxide or-higher 1,2-epoxides with amventional comonomers in-a conventional manner in aqueous suspension at temperaturesabove 85C using "free-radicahgenerating-initiators and adding, before or during polymerizatioman alkanolamine soluble in the organic phase of the suspension.

' Byoxyalkylation products of ammonia or primary or secondary amines we mean the reaction products '(known as'mono dior trialkanolamines) of ethylene monia or. primary or secondary aliphatic amines or their polyalkylene glycolderivatives formed by further reaction with alkylene oxide.

Suitable primary or secondary aliphatic monoor polyvalentamines for'thepurposes of the invention are for example those whose substituents are alkyl-radicals of froml to '20, in particular from 6 to--20, carbon atoms, aminoalkyl radicals offrom 2 to 8, in particular from 2 to 6, carbon atoms, cycloalkyl radicals having from5 to 7 carbon atoms in the ring, or their alkylsubstitutedderivatives having'from l to 20, in particular from i to 10', carbon: atoms in the alkyl substituent, and those (secondary) cyclic amines, in which the substituents together form an alkylene radical of from 4 to 8 carbon atoms which includes the amine nitrogen.

Suitable amines are,'for example, ethylamine, propyla- '"mine, .stearylamine, methyldodecylamine, dibutyl amine, piperidine, ethylene diamine and hexarnethylene diamine.

Accordingly, very'suit able alkanolamines are, for example, mono-alkanolamines such as 'N-decylethanolamine, -N-mthyl-ethanolamine, N-stearyl- A ethanolamine, N,N#bis-n dodecyl-ethanolamine and N,N-bis-cyclohex'ylpropanol(2)-amine, an example of an alkylene'oxide derivativeof a cyclic aliphatic amine being N-(2-hydroxyethyl)'-piperidine.

' Also suitable for themanufacture of styrene poly- I mers of the invention are dialkanolamines such as N,N- A bis(2-) hydroxypropyl n-dodecylamine and N,N-bishydroxyethyl-n-octadecylamine.

halogen-containing flame retardants at temperatures above 85C in order to shorten the polymerization time. If polymerization is carried out below the said temperature of 85C, very long polymerization times are, required but the 'styrene polymers obtained are capable of being processed into very good foams. For economical reasons-"however, preference must be r given to the process with shorter polymerization times.

It is therefore an object of the present invention to provide a process'whichavoids the above drawbacks of particles polymerized in thepresence of halogencontaining' flame retardants at temperatures above 85C.

We have now found" that particulate styrene polymers which are foamable (i.e., which contain foaming agent) and which have been prepared at polymerization temperatures above 85C and in the presence of flame retarda'nt organic halogen compounds can be processed into foam blocks which exhibit good fusion and whose *sides' do not tend to become concave, whenthey con- "tain a small amount of an oxyalkylation product of ammonia' or of a primary or secondary aliphatic amine,

'which oxyalkylation product is soluble in styrene or polystyrene. The said oxyalkylation products are also.

referred to as alkanolamines.

" A suitable'method of making such foamable styrene polymers is to polymerize styrene and, optionally, con- Finally, trialkanolamines which are suitable are those whose alk'ylenej'radical is long enough to ensure a certain degree of solubilityin the organic phase of the mixture to' be polymerized, for example tris-(N-Z- hydrOX ybutyD-amine.

In thepreparation of the alkanolamines used in the invention there are also obtained, due to substitution of t the hydroxyalk yl groups with further alkylene oxide, as

by-products polyalkylene glycol derivatives of the amines mentioned above having for example from 2 to 3 ether-linked alkylene glycol radicals instead of a hydroxyalkyl group. These compounds are also active on their own.

Itiappears"that-neither the chemical nature of the alkyl radical, when present, nor'thatof the alkanol radicalhas a'critical effect on the results achieved by the invention, provided the alkanolam'ine exhibits a certain degree of solubility in the monomer and the resulting polymer.

' The preparation of the alkanolamines is well known and does'not form part of the present invention.

The alkanolamines used inzthe present invention are employed in quantities of from 0.00001 to 1 percent,

\ inparticular-from 0.0001 to 0.1 percent, by weight based on the styrene polymer. Inall cases the amount 'used is'extremely small'compared with the amount of flame-retardant halogen compounds normally added. The substances may be added either to the organic phase or'to the aqueous phase or to the reaction mixture before, during or toward the end of polymerization. The amount to be used is governed by the nature and amount of halogen compound incorporated and by the temperature regime during polymerization and may be readily determined-by simple experiment.

Starting materials used for making the styrene polymers of the invention are monomer mixtures containing at least 50 percent by weight of styrene and optionally, as comonomers, for example a-methylstyrene, nuclearly halogenated styrenes, acrylonitrile, esters of acrylic or methacrylic acid with alcohols of from 1 to 8 carbon atoms, N-vinyl compounds such as N-vinyl carbazole or small amounts of butadiene or divinyl benzene.

Polymerization is advantageously carried out by the well-known pearl polymerization process at temperatures of from 85 to 130C.

Supension stabilizers which may be used are organic protective colloids such as polyvinyl alcohol, polyvinyl pyrrolidone and mineral suspension agents such as finely-divided tricalcium phosphate and barium sulfates.

Polymerization is initiated in known manner by means of one or more free-radical-generating substances. Examples of these are t-butyl perbenzoate, tbutyl perisononanate, di-t-butyl-peroxide, dibenzoyl peroxide and mixtures thereof.

Particularly suitable flame-retardant organic halogen compounds are bromine compounds such as the brominated oligomers of butadiene or isoprene having an average degree of polymerization of from 2 to 20. Bromination may be complete or partial. Examples of typical representatives are 1,2,5,o-tetrabromocyclooctane, 1,- 2,5,6,9,10-hexabromocyclododecane, brominated polybutadiene having a degree of polymerization of, say, from 3 to and l-(a, B-dibromoethyl)-3,4- dibromocyclohexane. The amount used is normally from 0.2 to 3 percent and preferably from 0.4 to 1.0 percent. It may be advantageous to add synergistic substances such as di-t-butyl peroxide, dicumyl peroxide and poly-p-di-isopropylbenzene.

The foaming agents used in the process of the invention are liquid or gaseous organic compounds which are non-solvents for the styrene polymer and boil at temperatures below the softening point of the polymer, for example aliphatic hydrocarbons such as propane, butane, pentane, hexane, cyclohexane or halogenated hydrocarbons such as methyl chloride, dichlorofluoromethane, 1,2,2-trifluoroethane and 1 ,1 ,2- trichloroethane. Mixtures of foaming agents may also be used. The amount of foaming agent used is normally from 2 to percent and preferably from 3 to 12 percent by weight of the monomers.

The expandable styrene polymers may also contain additives such as dyes, fillers, stabilizers and other flame retardants. They are produced in particulate form, for example in the form of beads, and generally have a diameter of from 0.1 to 6 mm, preferably from 0.4 to 3 mm. They are pre-expanded by known methods and completely expanded by heating in molds which are not gastight when closed so that the particles fuse together to form a foam article whose dimensions correspond to the internal dimensions of the mold used. Moldings obtained by foaming the styrene polymers of the invention are dimensionally stable, i.e., the sides show only a slight tendency to become concave after the molding has been removed from the mold.

EXAMPLE 1 Experiment (a) 1 W The following mixture is charged into a 1,000 l stirred autoclave purged with nitrogen:

450 1 of water having a hardness of 15 (German hardness) 230 g of sodium pyrophosphate 230 g of sodium acetate 560 g of magnesium sulfate 420 kg of styrene 4.5 kg of acrylonitrile 1.3 kg of t-butyl perbenzoate 150 g of t-butyl peroctoate 760 g of dicumyl peroxide 1.9 kg of 1,2,5,6,9,10-hexabromocyclododecane 6g of bis-hydroxyethyl-dodecylamine (equivalent to 0.0015 percent based on styrene).

The mixture is polymerized in the closed autoclave, with stirring, for 2 hours at C and then for 12 hours at 115C. While the mixture is being heated from 85 to 1 15C there is added 15 kg of a 10 percent solution of polyvinyl pyrrolidone having a K value of 85. 3 hours after a temperature of 115C has been reached, there is added 26 kg of n-pentane in the course of 15 minutes. Experiment (b) This is a repetition of Experiment (a) carried out under the same conditions except that 10 g of bis-hydroxyethyl-dodecylamine is used instead of 6 g thereof.

Comparative experiment This is a repetition of Experiment (a) except that polymerization is carried out without the inclusion of hydroxyethyl-dodecylamine.

Manufacture of foam blocks Aliquots of the three polymers produced in Experiments (a) and (b) and the comparative experiment are pre-expanded in flowing steam until they have a bulk density of 18 g/l. The pre-expanded samples are stored for 24 hours in the presence of air at room temperature, They are then completely expanded with wet steam in pressure-resistant molds measuring 100 X 50 X 100cm which are not gastight when closed to form foam blocks. The results are summarized in the follow ing Table.

Steam Degree of Example Pressure Steaming Quality of shrinkage 1 in Mold Period fusion at large sides (atm. (sec) (11) k gauge) (a) 0.8 20 0.8 0.6 20 90 0.3 0.5 20 B0 0.4 0.5 50 90 0.4 (b) 0.8 20 90 0.2 0.6 20 90 0.3 0.5 20 80 0.3 0.5 50 90 0.3 Comparative 0.8 20 35 4 experiment Thesteaming period is the time measured from the moment at which the stated steam pressure is reached in the mold to the moment at which the steam inlet valve is closed. "The quality of fusion is taken to be the ratio of the number of torn heads to the total number of beads at the fracture produced by forcibly breaking the block. '"Shrinkage of the blocks is measured 24 hours after removal of the block from the mold. It is determined by measuring the thickness of the block at the middle of a large side. The difference between the width of the mold at this point and the thickness of the block at this point, expressed as a percentage of the width of the mold, is the "degree of shrinkage".

EXAMPLE 2 Experiment (a) The following mixture is used:

450 l of water of a hardness of 15 (German hardness) 230 g of sodium pyrophosphate 230 g of sodium acetate 560 g of magnesium sulfate 420 kg of styrene 1.3 kg of t-butyl perbenzoate 300 g of t-butyl peroctoate 760 g of dicumyl peroxide 2.7 kg of 1,2,5,6,9,lO-hexabromocyclododecane 21 g of N-hydroxyethylpiperidine (equivalent to 0.005% based on styrene).

The mixture is polymerized with stirring in a closed 1,000 l autoclave for 2 hours at 90C, 1 hour at 100C, 1 hour at 110C and 6 hours at 115C. 1

One hour after a temperature of 90C has been reached, 15 kg of a percent solution of polyvinyl pyrrolidone (K value 87) is added to the mixture. 2.5 hours after a temperature of 1 C has been reached, 28 kg of n-pentane are metered into the mixture in the course of 15 minutes.

The resulting beads may be used for making moldings exhibiting good fusion and good dimensional stability. This is shown in the following table, which also lists the results of the following experiments.

Experiment (b) This is a repetition of Experiment (a) except that 7 g of N-hydroxyethylpiperidine is used instead of 21 g thereof. The foamable polystyrene beads obtained exhibit good processing characteristics.

Experiment (c) g This is a repetition of Experiment (a) except that the compound mentioned in Experiments (a) and (b) is replaced by 42 g (equivalent to 0.01 percent) of N- hydroxyethyl-dicyclohexylamine. This experiment also produces dimensionally stable moldings exhibiting good fusion.

Experiment (d) The sample is polymerized using 21 g (equivalent of 0.005 percent) of N-hydroxyethyl-dicyclohexylamine. The pre-expanded beads also produce dimensionally stable moldings.

Experiment (e) In a repetition of Experiment (a) the additive used in that experiment is replaced by 21 g (equivalent to 0.005 percent) of N,N-bis-hydroxyethylcyclohexylamine. After polymerization, it is possible to process the resulting heads into foam products exhibiting very good dimensional stability and fusion.

Experiment (f) Experiment (e) is repeated except that only 5 g (equivalent to 0.0013 percent) of amine is used. The moldings made from this product exhibit fairly good dimensional stability and fusion.

Experiment (g) Experiment (i) I The above procedure is followed except that 21 g (equivalent-to 0.005 percent) of dimethylethanolamine is used as additive. Dimensionally stable moldings are produced. 1 Experiment (h) v 1 The above procedure is followed except that-21 g (equivalent to 0.005 percent) of N,N,N- trihydroxybutylamine is used as additve. A product exhibiting good processing characteristics is obtained in this case, too.

The above procedure is followed except that 21 g (equivalent to 0.005 percent of N,N,N, N- tetrahydroxypropylhexamethylene diamine is used as additive. The product can be processed into dimensionally stable moldings exhibiting good fusion. Comparative Experiment I i In an experiment carried out under the same conditions but without the additive proposed by the invention there are produced beads which can only be processed into moldings exhibiting poor fusion and a relatively highdegree of shrinkage at the sides. Manufacture of foam blocks The expandable polymers produced in the above experiments of Example 2 were processed into moldings in thefollowing manner:

An aliquot was foamed in flowing steam until it had a bulk density of 18 gll and was then left in the presence of air for 24 hours. The pre-expanded sample was then completely foamed. with steam in a pressureresistant mold'measuring 100 X 50 X 100 cm which is i not gastight when .closed to form a foam block. The

most important properties of the moldings are given in the following Table.

Steam Degree of Example Pressure Steaming Quality of shrinkage 2 in Mold Period fusion" at large sides (atm. (s (9 gauge) (a) I 0.8 20 0.8 0.5 50 0.7 (b) 0.8 20 50 1.2 0.5 50 60 0.9 (c) 0.8 20 0.4 0.5 50 90 0.2 (d) 0.8 20 80 0.5 0.5 50 .90 0.2 (e) 0.8 20 70 0.8 0.5 50 80 0.5 (f) 0.8 20 60 1.3 0.5 50 80 0.7 (g) 0.8 20 55 1.5 0.5 50 60 1.0 (h) 0.8 20 80 0.4 0.5 50 90 0.2 (i) 0.8 20 65 1.0 0.5 v 50 90 0.5 Compar- I ative 0.8 20 25 4.5 experi 0.5 50 30 3.7 ment The steaming period is the time measured from the moment at which the.stated steam pressure is reached in themold to the moment at which the steam inlet valve is closed.

"The quality of fusion is taken to be the ratio of the number of torn beads to the total number of beads at the fracture produced by forcibly breaking the block. *Shrinkage of the blocks is measured 24 hours afier removal of the block from the mold. It is determined by measuring the thickness of the block at the middle of a large side. The difference between the width of the mold at this point and the thickness of the block at this point, expressed as a percentage of the width of the mold, is the degree of shrinkage.

We claim: 4

l. Expandable self-extinguishing styrene polymers containing from 0.2 to 3 percent by weight of a conventional flame-retardant organic bromine compound and from 0.00001 to l percent by weight, based on the styrene polymer, of an oxyalkylation product of ammonia at temperatures above C using free-radicalgenerating initiators, wherein from 0.00001 to I percent by weight, based on the styrene polymer, of an oxyalkylation product of ammonia or a primary or secondary aliphatic amine with ethylene oxide, propylene oxide or higher 1, 2 epoxides and contains from 1 to 3 oxyalkylene groups, which oxyalkylation product is so]- uble in the organic phase of the suspension, is added to the suspension before or during polymerization.

Column Column Column Column Column,

"WEED- STATES "FA it? OFFICE eERTmc -TE @F- mmm I aridlhat said Lettegrs Patent line lime

"additve" should read 6, insert" as 'Da'ted August 28, 1973 C It is certifiedtha't ertor up je ar s in fthe above-identified patent are hereby corrected as shown below:

19, '3upeusion" should read s n b after "is".

-- after "(a) insert insert 3 after "('b) insert after Yexperirhent". insert after "blocks eho uld read 7 I insert after "(a) ine'er't 3 M after "{b) inaerft g after "(0)". insert efter "((1)".

insert after "(e)".

insert after "(1?)".

insert 5 after (g)". insert after (h)".

-- additive F ORM PO-1050 (10-69) USCOMM-DC 60376-P69 v 11.5. GOVERNMENT PRINTING OFFICE 19 o-36s-3.u,

\ I r v page 2 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,755,209 Dated August-28, 1973 Inventor-(s) Ecm ard Einjgz e1; a1

, It is certified that error appears in the above-v-identified patent and that said Letters Patent are hereby correctedas shown below:

Column 6, line 11, insert after "(1)".

Column 6, line 1?, insert after "Experiment".

Column 6, line 23, insert after "blocks Column 7, we 3 "w 2nd 000. enoum read or Column 7, line 5-, "oxyalkyl-i-ation should read oxyalkylation Column 7, line 8, or" should read of Signed and sealed this 1st day of October 1974.

(SEAL) Attest:

MCCOY M. GIBSON JR. c. MARSHALL DANN Arresting Officer Commissioner of Patents uscoMM-Dc wan-ps9 U. 5. GOVERNMENT PRINTING OFFICE I9, 0-565-S3l.

F ORM PO-IOSO (10-69) 

2. A process for the manufacture or bromine compound-containing expandable styrene polymers as claimed in claim 1 by polymerizing styrene and, optionally, conventional comonomers in aqueous suspension at temperatures above 85*C using free-radical-generating initiators, wherein from 0.00001 to 1 percent by weight, based on the styrene polymer, of an oxyalkylation product of ammonia or a primary or secondary aliphatic amine with ethylene oxide, propylene oxide or higher 1, 2 epoxides and contains from 1 to 3 oxyalkylene groups, which oxyalkylation product is soluble in the organic phase of the suspension, is added to the suspension before or during polymerization. 